1) Field of the Invention
The present invention relates to a picture composing apparatus and method, and more particularly to a picture composing apparatus and method suitable for use in a system designed to convert/combine images acquired through the use of a plurality of image pickup means mounted in a motor vehicle for showing an image around the motor vehicle to a driver to support the driving at parking or the like. Furthermore, it relates to a picture displaying apparatus, a picture acquiring/warning apparatus and a motor vehicle position recognition/decision apparatus.
2) Description of the Related Art
So far, in such a type of picture composing apparatus, in the case of producing a wide-visual-field picture such as a panorama picture on the basis of a plurality of images by means of image composition, the plurality of images have been projected from the respective image pickup devices onto a common curved plane represented by a cylindrical surface and picked up by a virtual pickup device. This conventional procedure will be described hereinbelow with reference to FIGS. 14 to 15B.
FIG. 14 is an illustration of a composition procedure for a panorama picture 55 in which a scene 52 is taken through the use of two image pickup devices (not shown) mounted on a motor vehicle A to acquire images 53 and 54 which in turn, are projected onto a cylindrical surface 66. FIG. 15A three-dimensionally shows a procedure of projecting an image 62 taken by an image pickup device 61a and an image 63 taken by an image pickup device 61b for producing a composite picture on the cylindrical surface 66. A point 64 on the image 62 is projected to a point 67 and further projected to a point 69 on a composite picture plane 73 through a virtual image pickup means 72. In addition, a point 65 on the image 63 is projected to a point 68 on the cylindrical surface 66 and further projected to a point 70 on the composite picture plane 73 through the use of the same virtual image pickup means 72. FIG. 15B three-dimensionally shows a state projected onto a plane 71 perpendicular to an axis of the cylindrical surface 66. With the above-mentioned procedure, each point on the images 53 and 54 is map-converted to compose a picture such as the panorama picture shown in FIG. 14.
As an example of the above-described conventional technique, there has been known a technique disclosed in Japanese Unexamined Patent Publication (HEI) No. 5-14751. In addition, as examples of three-dimensional projection onto a plane, there have been known techniques disclosed in Japanese Unexamined Patent Publication (HEI) No. 6-20189 and in Japanese Unexamined Patent Publication No. 2000-134537. Still additionally, as an example of projection onto a spherical surface, there has been known a technique disclosed in Japanese Unexamined Patent Publication (HEI) No. 9-322040.
However, such conventional picture composing methods are designed to make one composite picture from a plurality of images taken by a plurality of image pickup devices mounted at positions different in projection center; therefore, discontinuous points 56a, 56b and 56c occur as shown in the composite panorama picture 55 of FIG. 14, which creates a problem in that difficulty is encountered in align the images at the joint between the different images. Moreover, in the case of the projection onto a cylinder, not only image distortions differ largely at positions near and apart from an image pickup device to make it difficult for a driver to seize a sense of distance, but also an image is largely distorted at a body end portion such as a bumper or fender of a motor vehicle as shown in a neighborhood image 57 on the panorama picture plane in FIG. 12, which makes it difficult to apply the methods to motor vehicle safety driving assist such as parking support.